Choose a large container, preferably terracotta not plastic, at least 18“(45cm) deep with adequate drainage holes. Put plenty of crocks, stones or gravel in the bottom to ensure good drainage and stand the container on feet or bricks to stop the drainage holes becoming blocked.
The best clematis compost is John Innes No.3 mixed with a good multi-purpose compost about 3 parts John Innes to 1 part multi-purpose. Plant the top of the clematis root deeper in the new container by about 3 inches.
Check container grown plants regularly for watering needs, however be careful not to keep them too wet over the winter, and ensure the pot is draining freely!
Each February remove an inch or two of compost from the top of the pot and replace with fresh compost to which a single handful of bonemeal has been added, and water in. For the best results, put 3 Westland Gro-Sure Tablets into the pot in March, then from April to the end of September we recommend using liquid tomato feed about once every two weeks.
Every four to five years root pruning may be necessary. During winter time when the plant is dormant take the pot off and cut away 2” - 3“ of root from the outside of the root-ball. Cut one third off the bottom, and re-pot with fresh John Innes No.3 compost.
Examples: Pink Flamingo
If young clematis plants are left unpruned they often produce very long single stems with the flowers produced only at the very top.
Unless the plant already has three or four healthy stems growing from the base, all newly planted clematis should be pruned back hard the first spring after planting. Cut back to just above a strong pair of leaf buds about 30cm (12in) above soil level. This will encourage multiple stems which can be trained to supports to give good coverage.
During the spring and summer, tie in new growth, spacing stems evenly on the support.
Established plants don't require regular pruning, but if necessary, prune immediately after flowering in mid- to late spring when the danger of frost has passed.